U.S. patent number 4,901,336 [Application Number 07/286,151] was granted by the patent office on 1990-02-13 for x-ray radiographic apparatus.
This patent grant is currently assigned to Kabushiki Kaisha Toshiba. Invention is credited to Masayuki Nishiki.
United States Patent |
4,901,336 |
Nishiki |
February 13, 1990 |
X-ray radiographic apparatus
Abstract
An X-ray radiographic apparatus including a solid-state image
sensor having a photoelectric conversion member and a transfer
member. A system controller stops supplying field shift pulses, and
a electric charge is not transferred from the photoelectric
conversion member to the transfer member, during X-ray irradiation
until a quantity of X-rays reaches predetermined value. One frame
image data from the solid-state image sensor just after X-ray
irradiating term is obtained. It is easy to obtain data
corresponding to one frame image which is of proper density. The
electric signal is read from the transfer member while the system
controller has stopped the supplying of field shift pulses. It is
possible to suppress an increase of dark current noise, and obtain
high quality X-ray image data.
Inventors: |
Nishiki; Masayuki (Tokyo,
JP) |
Assignee: |
Kabushiki Kaisha Toshiba
(Kawasaki, JP)
|
Family
ID: |
18121234 |
Appl.
No.: |
07/286,151 |
Filed: |
December 19, 1988 |
Foreign Application Priority Data
|
|
|
|
|
Dec 18, 1987 [JP] |
|
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62-320418 |
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Current U.S.
Class: |
378/98.8;
348/E5.086; 250/370.09; 378/98.2; 378/97 |
Current CPC
Class: |
H05G
1/60 (20130101); H05G 1/44 (20130101); H04N
5/32 (20130101) |
Current International
Class: |
H05G
1/00 (20060101); H05G 1/44 (20060101); H05G
1/60 (20060101); H04N 5/32 (20060101); H05G
001/64 () |
Field of
Search: |
;378/97,99 ;358/111
;250/370.09 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Church; Craig E.
Attorney, Agent or Firm: Cushman, Darby & Cushman
Claims
What is claimed is:
1. An X-ray radiographic apparatus comprising:
an X-ray tube for irradiating an object with X-rays;
an image intensifier for receiving X-rays transmitted through said
object and generating, an optical image indicative thereof;
solid-state image means for receiving an optical image from said
image intensifier and providing a signal indicative thereof, said
solid-state image means including a photoelectric conversion member
and a transfer member;
detecting means for sensing X-irradiation determining when
irradiation has reached a predetermined level; and
control means for stopping a supply of field shift pulses used as a
trigger to transfer an electric signal from said photoelectric
conversion member to said transfer member during the term of X-ray
irradiating.
2. An apparatus according to claim 1, wherein said control means
comprises means for causing the reading of data corresponding to
one frame image from said solid-state image sensing means just
after said X-ray irradiating term.
3. An apparatus according to claim 1, wherein said control means
control comprises means for causing the reading of said electric
signal from said transfer member during a term when said field
shift pulse is not being supplied.
4. An apparatus according to claim 1 further comprising an image
signal processor, and wherein said control means comprises means
for causing the storage of one frame of image data from said image
signal processor if a pixel value of specific region in a frame
memory exceeds a threshold level.
5. An apparatus according to claim 1 further comprising an image
signal processor, and wherein said control means comprises means
for causing the storage of one frame of image data from said image
signal processor if an added plural pixel value of specific region
in said frame memory exceeds a threshold level.
6. An apparatus according to claim 1 further comprising an image
signal processor, and wherein said control means comprises means
for causing the storage of one frame of image data from said image
signal processor just after said X-ray irradiating term.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an X-ray radiographic apparatus providing
a solid-state image sensing device for photographing an X-ray
radiographic image.
2. Description of Related Art
Generally, an automatic X-ray exposure unit is provided in an X-ray
radiographic apparatus to obtain an adequate density of the X-ray
picture. In this automatic X-ray exposure unit, X-rays transmitted
through an object is detected by detecting means, and if the
detected total quantity of X-rays reaches a predetermined value,
irradiation by X-rays is stopped. In this manner, adequate density
of the X-ray picture is obtained. One type of automatic X-ray
exposure unit uses an Image Intensifier (I.I.) as a detecting
means. It includes a phototimer in the rear of the I.I. to control
X-ray exposure time in accordance with a thickness of the object or
a portion thereof.
In a conventional X-ray radiographic apparatus, an image pick up
tube has been used to pick up image. However, an image pick up tube
has significant limitations relating to pixel number and reading
time. For this reason, solid-state image sensing devices, such as a
charge-coupled device (CCD) have come into used as a substitute for
the image pick up tube.
In general, one frame period is fixed to a predetermined period of
time, such as 1/30 sec., as in a TV camera. X-ray exposure time is
varied in accordance with the thickness of the object or a portion
thereof. Occasionally X-ray exposure time exceeds one frame period
(1/30 sec.). Accordingly, if the X-ray exposure time is controlled
automatically, sometimes the charge is read out before the detected
total quantity of X-rays reaches a desired level.
In this type of X-ray radiographic apparatus, it is necessary to
add plural frames to obtain adequate density of an X-ray image. The
use of plural frames makes the X-ray radiographic apparatus
complex.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an X-ray
radiographic apparatus which uses a solid-state image sensing
device capable of easily obtaining an adequate density of X-ray
image.
An X-ray radiographic apparatus according to this invention
comprises:
an X-ray tube for irradiating an object with X-rays,
an image intensifier for converting an image formed by X-rays
transmitted through the object into an optical image,
solid-state image sensing means for picking up an optical image
output from said image intensifier,
detecting means for detecting a X-ray irradiating term when the
X-rays is irradiated until a quantity of X-rays reaches
predetermined value,
control means for stopping irradiation of X-rays, the control means
including a field shift pulse power supply which is used as a
trigger to transfer a electric signal from a photoelectric
conversion member to a transfer member during the term of X-ray
irradiating.
Using the present invention, it is easier to obtain a proper
density of frame image data than it is by using conventional
devices.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic/block diagram an embodiment of the X-ray
diagnostic apparatus according to the present invention.
FIG. 2 is a diagram showing the characteristics of a solid-state
image sensing device used in the FIG. 1 embodiment.
FIG. 3 is a diagram explaining the operation of the X-ray
diagnostic apparatus shown in FIG. 1.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Embodiments of an X-ray radiographic apparatus according to the
present invention will be described hereinafter with reference to
the accompanying drawings.
FIG. 1 is a schematic/block diagram an embodiment of the X-ray
diagnostic apparatus according to the present invention. It
utilizes a solid-state sensing device. The X-ray radiographic
apparatus comprises X-ray tube 1, I.I. 2, optical system 3, TV
camera 5, A/D (analog-to-digital) converter 6, image signal
processor 7, D/A (digital-to-analog) converter 8, monitor 9, X-ray
controller 11, and system controller 12.
When a high voltage is applied to tube 1 from X-ray controller 11,
X-rays are irradiated from tube 1 onto an object P. X-rays
transmitted through object P are detected by I.I. 2. X-rays
transmitted through object P are converted by I.I.2 to a optical
image. The optical image is transmitted through optical system 3
including photo timer 10 to TV camera 5.
TV camera 5 includes a solid-state image sensing device 4 such as,
for example, a charge-coupled device (CCD), whereby the optical
image is picked up at rate of 30 frames per second. An analog video
signal from TV camera 5 is converted by A/D converter 6 to a
digital video signal.
The digital video signal is processed properly by image signal
processor 7. The processed digital video signal is converted by D/A
converter 8 to an analog video signal. A magnetic disc memory
device 13 is connected to image signal processor 7 for storing the
processed digital video signal. Monitor 9 displays a image based on
the analog video signal provided by D/A converter 8.
System controller 12 is coupled to X-ray controller 11, TV camera
5, A/D converter 6, image signal processor 7, D/A converter 8, and
monitor 9. System controller 12 controls irradiation timing, image
read-out and write-in timing, etc.
The characteristic of the solid-state image sensing device 4 will
be described with reference to FIG. 2. The solid-state image
sensing device 4 such as CCD has two kinds of fields A, B as a
photosensitive storage section. Each field is a frame storage
interlace mode. As shown in line (a) of FIG. 2, a video signal is
generated from TV camera 5 in synchronism with the Vertical Drive
Pulse (VDP) of one field per 1/60 second.
The solid-state image sensor 4 comprises of the photoelectric
conversion member and transfer member. The photoelectric conversion
member converts an incident optical image to an electric signal.
The electric signal is transferred to the transfer member when the
system controller 12 supplies a field shift pulse to the
solid-state image sensors 4. Then, the electric signal is stored in
the transfer member. System controller 12 supplies field shift
pulses to the each field A, B alternately in synchronism with the
VDP as shown in lines (b) and (c) of FIG. 2. As shown in line (d)
of FIG. 2, after transfer member receives the electric signal from
each field A, B each field A, B reverts to an optical storage
state.
The operation of the X-ray radiographic apparatus with the above
arrangement will be described with reference to FIG. 3. System
controller 12 supplies an X-ray irradiating trigger signal to X-ray
tube 1 through X-ray controller 11 (time tl). The X-rays irradiated
X-ray tube 1 and transmitted through object P is detected by I.I.
2.
X-rays are converted by I.I. 2 to an optical image. A portion of
the optical image is fed to photo timer 10 in optical system 3.
Photo timer 10 supplies a stop signal to system controller 12 when
the detected total quantity of X-rays reaches the predetermined
value. System controller 12 supplies an X-ray irradiating stop
signal to X-ray tube 1 through X-ray controller 11 (time t2).
According to this invention, the system controller 12 stops
supplying the field shift pulse during X-ray exposure term (from t1
to t2). After the image density becomes adequate, namely, the
detected total quantity of X-rays reaches the predetermined value
(t2), system controller 12 supplies a field shift pulse to
solid-state image sensor 4. Thus, it is possible to obtain an
adequate density of X-ray image by reading one image just after
time t2. An analog video signal fed through the solid-state image
sensor 4 is converted by A/D converter 6 to a digital video signal.
The digital video signal is processed properly by image signal
processor 7. The processed digital video signal is converted by D/A
converter 8 to an analog video signal. Monitor 9 displays a image
based on the analog video signal converted by D/A converter 8.
Even though the field shift pulse is stopped, a vertical drive
pulse is supplied. Thus, the electric signal (charge) is not
transferred from the photoelectric conversion member to the
transfer member, but the electric signal (charge) from the transfer
member is read continuously. Accordingly, it is possible to
suppress a increase of dark current noise, and obtain high quality
image by reading one frame image.
Magnetic disc memory device 13 is connected to image signal
processor 7. System controller 12 supplies instructions to image
signal processor 7 and magnetic disc memory device 13. Magnetic
disc memory device 13 stores one frame image just after an X-ray
irradiating term. According to this invention, it is possible to
store one frame image except frame images which are not included
X-ray image information.
It is desireable to obtain as an output signal from the solid-state
image sensor 4, a video signal which includes X-ray image
information (without noise). It is very efficient to use one frame
image just after X-ray irradiating term.
In aforementioned embodiment, one frame image just after X-ray
irradiating term is regarded as a video signal which includes X-ray
information. Image signal processor 7 provides frame memories. If a
pixel value of specific region or added plural pixel value of
specific region in the frame memory exceeds a predetermined value,
one frame just after that time is regarded as a video signal which
includes X-ray information and magnetic disc memory device 13
stores this one frame image data.
While this invention has been described in connection with what is
presently considered to be the most practical and preferred
embodiment, it is to be understood that the invention is not
limited to the disclosed embodiment, but, on the contrary, is
intended to cover various modifications and equivalent arrangements
included within the spirit and scope of the appended claims.
* * * * *